Such stents or implantable catheters, which can be inserted in a body cavity, a vessel or the like, can be made from plastic or an inert metal, such as steel or nickel-titanium alloys. Such stents are in particular known as endovascular or endoluminal stents or intraluminal tubes. The stents are e.g. used for widening the ureter in the prostate region in the case of benign prostate hyperplasia (BPH) or in the case of sclerotic blood vessels for widening and keeping open the same. The stents have material areas and gaps between them. Thus, the parietal tissue of the organ kept open can grow round the stent. Stents can have a spiral construction or can be in the form of a helically wound coil. They can also be made from woven, knitted or braided wire or plastic material. Such stents can have memory characteristics, such as e.g. occur with certain nickel-titanium alloys (nitinol).
A problem with such stents is their limited bendability, particularly on introducing through narrow organs, such as blood vessels, at the point where a widening can take place. There is a risk that on bending the stent bends in in the center as a result of the action of axially vertically directed forces, in that its cross-sectional area is reduced in the direction of the acting forces, but is widened perpendicular thereto and to the axial direction thereof. This can make insertion more difficult and can also damage the surrounding tissue, particularly if the stent is to be inserted in a bend area of the vessel or the like. Stents are relatively stiff and inflexible. This more particularly applies with stents having a rhombic structure, which are e.g. produced by cutting from nickel-titanium sheeting and have memory characteristics.